PURPOSE: To facilitate the manufacture, maintenance, and alteration of software system by providing the a kernel which communicates with respective ports and executes background processes that the ports request.

CONSTITUTION: A message is handled according to an analysis of the message, and an interface process which sends an internal message of a component 1L out is generally executed according to the message. This message is normally in the shape of background process order sent to the kernel 1N of the corresponding component 1L so as to perform a background process executed with parameters included in the received external message. For example, a port 1S2 responds to external message or event and a port 1S2 checks the activity state of the kernel 1N when receiving the external message which requires a background process by the kernel 1N.